SALAMANDRA 56(1): 39–47 Activity, habitat use and lingual lure behavior in a South American snakeSALAMANDRA 15 February 2020 ISSN 0036–3375 German Journal of Herpetology A fisherman’s tale: Activity, habitat use and the first evidence of lingual lure behavior in a South American snake Conrado Mario-da-Rosa1, Arthur Diesel Abegg2,3, Leandro Malta-Borges1, Alexandre Ferreira Righi4, Paulo Sérgio Bernarde5, Sonia Zanini Cechin1 & Tiago Gomes dos Santos1,6 1) Programa de Pós-Graduação em Biodiversidade Animal, Universidade Federal de Santa Maria, Av. Roraima, 1000, Santa Maria, Rio Grande do Sul, Brazil 2) Laboratório Especial de Coleções Zoológicas, Instituto Butantan, Av. Vital Brasil, 1500, São Paulo, São Paulo, Brazil 3) Programa de Pós-Graduação em Zoologia, Instituto de Biociências, Universidade de São Paulo, Travessa 14, Rua do Matão, 321, 05508-090, São Paulo, São Paulo, Brazil 4) Museu de História Natural e Jardim Botânico da Universidade Federal de Minas Gerais, R. Gustavo da Silveira, 1035, Belo Horizonte, Minas Gerais, Brazil 5) Laboratório de Herpetologia, Centro Multidisciplinar, Campus Floresta, Universidade Federal do Acre, Cruzeiro do Sul, Acre, Brazil 6) Universidade Federal do Pampa, Campus São Gabriel, Av. Antônio Trilha, 1847, São Gabriel, Rio Grande do Sul, Brazil Corresponding author: Conrado Mario-da-Rosa, e-mail: [email protected] Manuscript received: 23 August 2019 Accepted: 25 November 2019 by Arne Schulze Abstract. Literature data suggests that Thamnodynastes strigatus (Serpentes, Dipsadidae) is a snake that actively forages for anurans near waterbodies, using several microhabitats for this activity (e.g., shrubs, soil, and water). However, herein we present dissonant data previously known to the species, both concerning type of prey and foraging strategy. A total of 72 observations were performed exclusively at night, when snakes were in vegetation near streams in 93% of the cases. Among these observations, 41 were active snakes, and most of them (97%) were in an ambush position on the vegetation, peering at fishes. On two occasions, the snakes used a lingual lure behavior in order to attract fishes. This is only the sixth species in which this behavior has been observed, and the first in South America. Therefore, we provide additional data on T. strigatus habitat activity and habitat use, as well as unpublished data on ambush and lingual lure behavior for the Neo- tropical genus Thamnodynastes. Key words. Thamnodynastes strigatus, nocturnal activity, ambush behavior, sub-arboreal, Uruguayan savannah. Introduction evolutionarily plastic and can be shaped by prey abundance and behavior (Vitt & Caldwell 2014). Some snakes, in Data on the feeding ecology of any species aids in the un- association to the ambush-hunting method, use attractive derstanding of its natural history, ecological requirements exhibitionist displays to maximize prey capture success and the diverse approaches involved in the search for food (Sazima 1991, Welsh & Lind 2000, Hansknecht 2008), and habitat use (Al-Sadoon & Parray 2016). In snakes, the also termed mimetic-aggressive behaviors (Glaudas & most commonly observed criteria for habitat selection and Alexander 2017). However, although visible growth in use are the selection of better hibernation sites (Reinert recent decades is noted (Bernarde et al. 2000b, Hart- 1993), safer refuges for predator avoidance (Martins 1993, mann & Marques 2005), studies on snake feeding ecology Webb & Whiting 2005), or prey distribution and availabil- are still scarce in the Neotropical region (Andrade et al. ity (Madsen & Shine 1996). Notably, the foraging environ- 2010, Braz & Marques, 2016), when compared to temper- ment is strongly related to the availability and abundance ate northern hemisphere regions and the Australian conti- of potential prey (Bernarde et al. 2000a). Concerning ba- nent (Shine 1988, Welsh & Lind 2000, Gibbons & Dor- sic hunting strategies, snakes may use the ambush meth- cas 2004, Hansknecht 2008). od (Glaudas & Alexander 2017), the active search (Ber- The genus Thamnodynastes Wagler, 1830 comprises 20 narde et al. 2000a) or even both, in different situations species distributed throughout South America (Franco et (Martins & Oliveira 1998). These foraging strategies are al. 2017). Thamnodynastes strigatus (Günther, 1858) is a © 2020 Deutsche Gesellschaft für Herpetologie und Terrarienkunde e.V. (DGHT), Mannheim, Germany Open access at http://www.salamandra-journal.com 39 Conrado Mario-da-Rosa et al. medium-sized snake that reaches about 800 mm in length etation; and height (cm) of the specimens perched on the (Giraudo 2001) and occurs in Argentina, Paraguay, Uru- substrate in relation to the water or soil surface, measured guay, and southern and southeastern portions of Brazil with a millimeter measuring tape); (2) activity pattern (ac- (Borges-Martins et al. 2007). Its diet consists of fishes, tive = specimens hanging on branches, perpendicular to lizards, mammals and, predominantly, anuran amphibians the water surface (ambush position) or in motion; inac- (Bernarde et al. 2000b, Ruffato et al. 2003). The only in tive = specimens that remained static on a substrate, with situ feeding ecology study concerning T. strigatus report- no signs of activity for at least 15 minutes) (adapted from ed some anuran predation events and concluded that the Di-Bernardo et al. 2007); (3) air temperature (°C), deter- species is an active forager that exploits different types of mined using a digital thermo-hygrometer. Monthly aver- substrates at night (ground, vegetation, water body surface age maximum and minimum temperatures were obtained and interior) and uses undergrowth vegetation for daytime from the Instituto Nacional de Meteorologia (INMET) rest (Bernarde et al. 2000a). However, we found a T. stri­ (http://www.inmet.gov.br/portal/) for the Alegrete mete- gatus population in the Uruguayan Savannah ecoregion orological station, 78 km distant from the study area. These (sensu Olson et al. 2001), southern Brazil, which differs averages were used to test the relationship between the remarkably concerning previously known hunting strate- abundance of snake encounters and temperature extremes gies and food items. Therefore, the aim of the present study (minimum and maximum). is to describe this population’s hunting strategies, habitat In order to describe T. strigatus ambush-hunting behav- use and activity. ior, we opted for ad libitum observations (Altmann 1974), of active individuals and better observation conditions at each sampling (i.e. allowing for a nearby observation site Material and methods with the least possible visual obstruction). Video record- Study site ings were made in order to document and characterize the duration of the displayed behaviors, using a Nikon Coolpix The fieldwork was performed in the Serra do Caverá re- p510 camera. Additionally, the snout–vent length (SVL, to gion, in the east portion of the geomorphological unit the nearest mm) and sex of the individuals (determined named Cuesta de Haedo (Pilau 2011). This area is locat- with eversion of hemipenis) observed in predation events ed between the municipalities of Rosário do Sul and San- were also recorded. tana do Livramento, in southwestern state of Rio Grande do Sul (Brazil), in the Uruguayan Savannah ecoregion (30°21’41.16” S 55°15’53.15” W). The region is composed of Statistical analyses a natural mosaic that includes steep elevations with flat or round ridges and flooded lowlands, both with the predom- Student’s t-test was applied to assess possible differenc- inance of grasslands, besides arboreal-shrub vegetation re- es in the mean values of the behaviors exhibited by the stricted to stream banks and some hill slopes (Robaina et snakes. Linear regressions were used to evaluate the re- al. 2015). The climatic seasonality of the region is marked, lationship between snake abundance and air tempera- with the four well defined seasons. The thermal ampli- ture (mean monthly minimum and maximum). An alpha tude is accentuated, ranging from -3°C during the winter < 0.05 was established for all statistical tests. All statisti- to 39°C during the hottest months of the year (Wrege et cal analyses were carried out with the R software (R Core al. 2012). Although the rainfall in the region is high and Team 2015). constant throughout the year (1400–1700 mm; Rossato 2011), a drop-in surface water availability (rainfall-eva- potranspiration) is noted in the summer months (Wrege Results et al. 2012). Activity and habitat use A total of 72 T. strigatus specimen observations were made Sampling and data collection throughout the samplings, distributed during the hottest months of the year (November to April). A positive and sig- Monthly samplings were carried out during one year, from nificant relationship between the number of observations August 2017 to July 2018 (except in June, due to logistical and the average minimum and maximum temperature was problems), with each field trip lasting 5–6 days. Search- observed (R²aj = 0.45; p <0.05; R²aj = 0.45; p <0.05, respec- es for specimens were performed using the visual search tively). A significant difference (t = 2.49, p <0.05) regarding method (McDiarmid et al. 2012). After sighted, the snakes temperature and the respective snake activity pattern was were monitored at a minimum distance of 1.5 m, in order noted, since active individuals were found in higher tem- to minimize possible disturbances due to the presence of peratures (x = 22.93±0.43; n = 45) compared